Oxidative stress responses of Mytilus galloprovincialis to acute cold and heat during air exposure

We investigated the impacts of acute cold and heat exposure on mortality, oxidative stress, antioxidative and stress response, and apoptotic activation in gill tissue of Mytilus gallopromnaahs. Our results showed that both cold (4 degrees C) and heat stress (35 degrees C) resulted in high mortality. Reactive oxygen species increased significantly after cold stress at 4 degrees C and heat stress at 30 degrees C (P < 0.01). In addition, both malondialdehyde content and antioxidative enzyme (SOD, CAT and GSH-Px) activities increased significandy after both cold and heat stress (P < 0.05). However, the transcripts of Hsp70 up-regulated only after heat stress. Western-blot analysis of gill extracts showed that the phosphorylation levels of p38-MAPK were enhanced only at the beginning of cold and heat stress, but elevated activation levels of caspase-3 were observed throughout a 24-h recovery period. Our results suggested that extreme cold and heat air exposure resulted in oxidative stress in the gill tissue of the mussels. The antioxidant enzymes are crucial under both cold and heat exposure, while Hsp70 is induced by heat stress. It seems that p38-MAPK plays a key role in the early response to both cold and heat stress and that apoptosis might be activated in the gill tissue of M. gallopromnaahs.